Help with my basement toilet rough in situation!

I have an issue with my basement toilet rough-in. As in the toilet pipe was loose - in fact, it came right out with the slightest tug. It was ABS going down to CI. How do I connect a new toilet pipe? I have roughly 4 5/8" to work with - but I'd like to install an offset flange to allow for a standard 12" rough in from the wall. It was originally 10 1/2.

I built a raised sub floor which gives me room for the offset flange but I am still undecided on how to connect the ABS to the CI. The CI is down in the concrete. I'll go take some pics and post back in a few.

1) install a manhoff fitting and pour a lead joint (not very homeowner friendly here).

2) install a compression donut of the appropriate size, soap up the gasket and push the ABS into place (more like drive the ABS pipe in using a piece of wood and a hammer)...see image of the compression donut. The ABS pipe edge should be slightly beveled at the end to push in and seat properly.

3) Use soil seal...see image. Some people install an oakum material under the soil seal. I can't say what I would do as I always lead in a manhoff and go that way most of the time.

The 2nd option is probably most homeowner friendly...gasket and plumber's soap available at any plumbing supply house!

As it turns out, my original evaluation was all wrong! I went to clean out the hole with a wire brush and discovered that the hub of the CI actually goes right up to be level with the concrete - it was pretty rough looking so I thought the pipe ended under the concrete. After a nice buffing with a wire wheel it is clear that the pipe is indeed up where it should be.

Annoyingly, I tried desperately to find a donut but every single plumbing store I went to gave me a blank stare. Using brand names and even pictures. I didn't find a single place that carried them.

I know you're trying to save a few dollars, but this is one connection you don't want to come loose in the future. I would suggest you bite the bullet and hire a plumber to lead a flange to the CI at the proper height. The other methods may work fine, but you never know. Of course it's easy for me to spend your money, LOL.

If you use the donut, ensure the pipe is seated properly, and the CI is clean, then anchor the flange to the concrete with the appropriate fasteners, it will be solid. But, if the CI is as rusted as it looks, you may not be able to clean it up enough to get the donut to seal properly. Hard to say without being there. There's normally no pressure there, so the risk is only if and when there's a backup (clog).

Shame...pretty common in my area! If the local plumbing supply store doesn't have them (still hard to believe) then you may do well to check at the local home depot...fernco makes these, too and most home depots seem to carry them. If you do find a donut and you find that it is a sloppy fit it is possible that you have an EXTRA HEAVY (XH) cast iron hub (as opposed to service weight (SV) cast iron in most homes) there in the ground and you will need to find an XH donut, go with the soil seal, or hire a pro. to pour a lead joint.

For what it is worth I have used soil seal plenty of times on cracked tubs and have packed a few cast iron joints over the years...always amazed at just how hard this stuff dries, so you shouldn't need to worry much if you pack the joint well and secure the flange properly, OK?

Fernco sells a huge number of the donuts in various sizes. Most places only stock a couple, if that, for the sizes usually used in your area. But, since there is no standard on the size of a bell on a CI fitting, each foundary made their own choices. That's why Fernco makes so many in slightly different dimmensions. The inside hole is standard, as the PVC or ABS has a standard, but the OD varies by the foundry and often the year of manufacture. It is important to get the proper size to ensure the seal is good. Too small, and it won't seal (OD); too large and you might get the plastic pipe in, but you might not, either. Just like the three bears...you want 'just right'!

The rust was just surface rust - a quick buffing with a wire brush cleaned it right up. I hope to pack it today, and will report back when it's done.

Also since Gary Swart put some doubt in my mind I have taken extra precautions and ran two electrodes from a water alarm I have under the sub-floor to the area around the toilet. If it leaks I will know - and clean it out and hire a pro. I'm a poet and I didn't even know it.